1. Field of the Invention
The present invention relates to a method for driving a display, and more particularly to a data driving system and method for driving a display, wherein an offset in the driving voltage is eliminated by the first polarity (positive) offset and the second polarity (negative) offset in space and time.
2. Description of the Related Art
Referring to FIG. 1, a panel 11 (e.g. a liquid crystal panel) is driven by a plurality of data driving systems 10 (e.g. two data driving systems in the figures) to display images. Each data driving system 10 obtains a plurality of reference voltages VR1˜VRm from a reference voltage supply (not shown), and receives the pixel values over the channels ch1˜chn so as to convert the pixel values into the analog driving voltages, and sends in parallel the driving voltages on these channels to a set of corresponding data lines on the panel 11 according to the scanning timing and data polarity inversion timing. Each data driving system 10 comprises a gamma voltage supply 101, a D/A converter (DAC) 103, an output buffer 105 and a multiplexer 107.
The gamma voltage supply 101 comprises a plurality of operational amplifiers OP1˜OPm and resistors R1˜Ri. Each of the operational amplifiers OP1˜OPm is used as the input buffer for each of the reference voltages VR1˜VRm, in order to prevent the change of the reference voltage caused by its load. After being received and output by the buffers, the reference voltages are divided by means of the resistors R1˜Ri, thus generating two sets of gamma voltages with positive and negative data polarity respectively, such as V0+˜V63+ and V0−˜V63−, and then these gamma voltages are input to the D/A converter 103. The D/A converter 103 may output a corresponding gamma voltage of the two sets of gamma voltages for each channel, based on the pixel value and data polarity of the channel. The voltage output by the D/A converter 103 is then output as a driving voltage via the output buffer 105. The multiplexer 107 is used to switch the connection between the output channels of the data driving system and the panel's data lines in conjunction with the data polarity inversion timing, so as to achieve different driving modes, including frame inversion, row inversion, column inversion, dot inversion or two dot lines inversion and the like.
However, since the outputs of the operational amplifiers have an inherent positive or negative polarity offset, the gamma voltages output by the gamma voltage supply also have the same polarity offset, thereby the final driving voltages produced have the same polarity offset, too. Moreover, as the offset output from one operational amplifier is different from that of another, and the gamma voltage supply in each data driving system employs a group of operational amplifiers respectively, the offset of the driving voltages generated in each module is different. Therefore, the distinct luminance or color difference occurs between the vertical band regions driven by different data driving systems on the panel due to the different offsets in the driving voltages of each module, thus forming the so-called “band mura”.
Therefore, it is necessary to provide a novel and inventive data driving system and method to solve the above problems.